Newsletter Pretoria Centre ASSA August 2018 Page 1 of 15

NEWSLETTER AUGUST 2018

TABLE OF CONTENTSAstronomy- related articles on the Internet 2

Astronomy-related images and video clips on the Internet 3

A call for speakers 3

Chairman’s report for meeting on 25 July 2018 4

Total lunar eclipse on 27 July 2018 - spectra 5

Photographs of the total lunar eclipse on 27 July 2018 8

NOTICE BOARD 9

Feature of the month: Life on Europa? 9

July 20th 2018 observing evening report 10

Summary of presentation to be given on 22 August under “What's Up?” 11

All planets in same half of solar system on 17 August 2018 14

Pretoria Centre committee 15

Astronomy basics: Celestial Sphere, Ecliptic, and the Constellations 15

Summary of “Beginner’s Corner” to be presented on August 22nd 2018 15

NEXT MEETINGVenue: The auditorium behind the main building at Christian Brothers College (CBC), Mount

Edmund, Pretoria Road, Silverton, Pretoria.Date and time: Wednesday 22 August at 19h15. Programme:➢ Beginner’s Corner: “The Great Conjunction of December 2020” by Michael Poll *.➢ What’s Up? by Percy Jacobs.----------------------------------- 10-minute break — library will be open. --------------------------------➢ Main talk: “Investigating exoplanet atmospheres” by Jose da Silva.➢ Socializing over tea/coffee and biscuits.

The chairperson at the meeting will be Bosman Olivier.* See page 15 for a summary of his talk.

NEXT OBSERVING EVENINGFriday 17 August from sunset onwards at the Pretoria Centre Observatory, which is alsosituated at CBC. Turn left immediately after entering the main gate and follow the road.

Newsletter Pretoria Centre ASSA August 2018 Page 2 of 15

Astronomy- related articles on the Internet

Astronomers see mystery explosion 200 million light-years away. Astronomers have anotherfascinating mystery on their hands, as they try to figure out the nature of a huge, unusualexplosion – labelled AT2018cow, nicknamed The Cow by astronomers – in a distant galaxy.http://earthsky.org/space/mystery-explosion-at2018cow-nicknamed-the-cow?utm_source=EarthSky+News&utm_campaign=24d0f9a2f0-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-24d0f9a2f0-394671529

Astronomers capture 1st confirmed image of newborn planet. http://earthsky.org/space/1st-confirmed-image-newborn-planet?utm_source=EarthSky+News&utm_campaign=b8dbe2d92d-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-b8dbe2d92d-394671529

Will we recognize life on a distant world? Scientists from NASA considered how to interpretthe presence of biosignatures, should we detect them on distant worlds.http://earthsky.org/space/alien-life-biosignatures-nexss-5-review-papers?utm_source=EarthSky+News&utm_campaign=5b71c79a74-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-5b71c79a74-394671529

Astronomers discover 10 new moons for Jupiter. Jupiter has 69 + 10 = 79 known moons.http://earthsky.org/space/10-new-moons-discovered-jupiter-1-oddball?utm_source=EarthSky+News&utm_campaign=c78bbe3455-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-c78bbe3455-394671529

Innovative new instrument to seek habitable worlds. Up to 19 July 2018, 3774 exoplanetshad been found. As more and more exoplanets are discovered, the technology used to find themkeeps advancing as well. http://earthsky.org/space/new-instrument-will-help-find-habitable-exoplanets-orbiting-red-dwarf-stars?utm_source=EarthSky+News&utm_campaign=68a58f9990-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-68a58f9990-394671529

5 things we know – and 5 we don’t – about ‘Oumuamua. Mysterious ‘Oumuamua is the 1stconfirmed interstellar object to pass through our solar system. http://earthsky.org/space/5-things-we-know-dont-about-oumuamua?utm_source=EarthSky+News&utm_campaign=68a58f9990-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-68a58f9990-394671529

Subsurface lake discovered on Mars? ESA’s Mars Express spacecraft has discovered the firstevidence for a subsurface liquid water lake on Mars. http://earthsky.org/space/mars-express-spacecraft-finds-evidence-of-subsurface-lake-on-mars?utm_source=EarthSky+News&utm_campaign=81903a50dc-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-81903a50dc-394671529

Most Mars dust comes from one place. http://earthsky.org/space/mars-dust-source

MeerKAT radio telescope unveiled. MeerKAT is the world's largest radio telescope and willlater be integrated into the SKA‚ which will be 50 to 100 times more sensitive than any other radiotelescope on Earth.https://www.timeslive.co.za/news/sci-tech/2018-07-13-from-the-northern-cape-to-infinity-and-beyond-meerkats-amazing-powers/

https://www.timeslive.co.za/news/sci-tech/2017-12-25-telescopes-in-southern-africa-will-peel-back-the-universes-secrets/

Newsletter Pretoria Centre ASSA August 2018 Page 3 of 15

Astronomy-related images and video clips on the Internet

Hubble catches views of a jet rotating with comet 252P/LINEAR.http://hubblesite.org/news_release/news/2016-14

Beautiful images of Perseid meteor shower 2018.https://www.msn.com/en-za/news/national/watch-students-go-on-rampage-at-ukzns-westville-campus/ar-BBLRuRS?li=AAaxc0E&ocid=spartandhp

A call for speakers

A call is hereby made to members to come forward and give presentationsat our monthly meetings under “Beginner’s Corner”. Let me (your newslettereditor) know if you are willing to do it. Here is a list of 10 topics to choose from:

1. Movement of the sun and the seasons. – the ecliptic and the analemma.2. Day and night, including solar day and sidereal day.3. Movement of the Earth around the Sun on an annual basis in order to

explain north-south movements of the Moon to account for its phases andits daily movement across the sky. Libration.

4. Rising and setting of the stars and why different stars are seen at differenttimes of the year.

5. The concept of celestial poles and the special case of circumpolar stars.Effect of change in latitude. How to find the south celestial pole. Obtain acompass direction from the stars.

6. Explain magnitude as applied to the brightness of celestial objects and the factors affecting apparent brightness. List the brightest stars, comparing apparent magnitude with distance.

7. Factors affecting the varying magnitudes of the planets. Albedo. 8. Lunar geology (properly called selenology).9. Crater morphology – simple and complex craters with examples.10. Lunar geography (‘selenography’). Ω

Newsletter Pretoria Centre ASSA August 2018 Page 4 of 15

Chairman’s report for meeting 25 July 2018 - by Johan SmitThe July meeting was well attended considering that it included the

AGM on its agenda. Johan Smit chaired the meeting and led the AGM thattook place instead of the usual “Beginner’s Corner” presentation. Theminutes of the AGM is sent with this newsletter. Please read and comment ifyou notice any errors or omissions.

During the AGM special mention was made of these members thatregularly participate in our outreach events. They deserve special thanksfrom me and the committee. Here they are, in no particular order:Michael Poll, Johan Smit, Percy Jacobs, Wessel Nel, Bosman Olivier,Nigel Rotherham, Rudolph Strydom, Neville Young, Danie Barnardo,Fred Oosthuizen, Anton Grobler, Johan Jordaan, Waldo Koen, DawieVenter and Andy Overbeek. At some of these events non-members fromthe ATM class, Bill Potgieter and Etsou Takayanagi joined us.

I thank all of these people for supporting the work of ASSA Pretoria.After the AGM, Percy Jacobs inspired us with what is up in the sky in

August. He inspired the members who plan to attend the upcoming Karoostar party.Instead of risking an invited speaker with a below average audience a videoarticle about the Apollo Lunar landing program was shown.

This episode concentrated on the Lunar Excursion Module (LEM).Apart from the interesting facts about the design of the module there wasalso a lot of fascinating data about space craft design in general.

One aspect that was cleared up was why these craft is built in superclean rooms.Dust stay in the air in micro gravity and thus cause health risks for theastronauts making it very important that the craft is very clean and dust free.

Feedback from the audience indicates that they enjoyed this movie asmuch as they enjoy a real speaker.

The meeting ended with the usual refreshments and interestingdiscussions. Ω

Newsletter Pretoria Centre ASSA August 2018 Page 5 of 15

Total lunar eclipse on 27 July 2018 - spectra– by Percy Jacobs (Amateur Astronomer)

This story was initiated by a request from Tim Cooper who needed this data for aproject he is working on regarding the Lunar Eclipse

It is important to note that during a total lunar eclipse, the moon takes on a darkred color because it is being lighted slightly by sunlight passing through the Earth'satmosphere whose ray paths are bent because the light scatters off the gas particles inthe Earth's atmosphere. It turns out that the physics of light scattering tells that, for theconditions of the Earths atmosphere, blue light (high frequency) is scattered more thanred light (lower frequency). Blue light is scattered too much to be seen at the smallangles of scattering needed to illuminate the moon in a total eclipse. Only the red lightray paths are scattering appropriately. This particular scattering is called "RayleighScattering" and is the SAME REASON THAT THE SKY IS BLUE IN THE DAY, but thesun looks red at the horizon! The blue light is scattered more and so our more directview of the sun means that we see the light rays which are not bent. If the Earth'satmosphere is particularly cloudy or dusty (e.g. from Volcanos) then the moon can bedarker as some of the light is further absorbed by the atmosphere.

One more effective method to investigate the optical properties of medium andhigh atmosphere layers is to measure the light absorption, emission and scattering bythe tangent ray path with different tangent point altitudes. This case the most part of thepath has an almost the same altitude, the influence of higher layers with less density issufficiently smaller than in the case of zenith measurements from the ground. Such pathhas larger optical depth, this gives us the possibility to detect small optical featuresbetter than by other methods. Tangent radiation measurements are possible on theground if we observe the body moving through the shadow of the Earth. This body canbe the artificial satellite of the Earth, this case we will measure one extinction profileabove the definite location on the planet. But if the shadow is crossed by the Moon, thedifferential surface photometry will give the possibility to build the vertical profile ofextinction coefficient along the part of the Earth’s limb. The size of this part will dependon the path of the Moon through the shadow (or umbra). (credit to Oleg S. Ugolnikova,b,* and Igor A. Maslov a,c - Atmospheric Aerosol Limb Scanning Based on the LunarEclipses Photometry)

Continued on next page.

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Eclipse timing

1. Umbra touch, start – 20:242. Halfway into Umbra – 21:003. Complete in Umbra but still touching the edge of the Umbra – 21:304. Total Eclipse – 22:24

Eclipse spectra taken

1. 18:55 (4sec’s / ISO 100)2. 21:50 (270 sec’s / ISO 3200)3. 22:07 (300 sec’s / ISO 3200)4. 22:25 (300 sec’s / ISO 3200)

Before eclipse

During eclipse

From the above, the following is clearly seen and concluded;1. The blue side of the spectrum is not seen and therefore scattered. Only the red

side of the spectrum is seen2. The broadening of the Telluric O2 is seen & absorption is greater3. The broadening of the Hα Balmer line is seen4. The Sodium Doublet Lines are also broadened & remain visible throughout5. Telluric 02 line broadens as the moon moves into the Umbra6. A feature at 648.2 nm is very prominent as the moon moves through the eclipse.

This feature is not prominent before the eclipse. It remains at the same intensitythrough the 3 phases measured.

Continued on next page.

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Spectroscope slit location

Equipment1. Celestron CGEM DX tracking mount2. Celestrom 80mm refractor3. Canon 650D (spectra image taking)4. ZWO ASI 130MM (mono) (slit position tracking)5. LOWSPEC 600L/mm spectrograph

Processing1. BASS Software2. Images processed – dark & flat adjusted, tilt, slant, binned, calibrated, IR corrected, atmosphere extinction adjusted3. Used Std Reference Spectrum, Pickles, G2V, for IR Correction of the 4 imaged

spectra

Conclusion1. Small telescopes & small spectrographs, are effective for spectroscopy &

photometry (confirmed as per paper issued by Richard Berry on this subject)2. The equipment used is capable of determining the gross features of the

transmission spectrum of Earths atmosphere. Therefore, within the budgets and capabilities of Amateurs.

3. The primary reddening is due to Rayleigh and aerosol scattering4. The broad, fuzzy depression centered at 630 nm suggests the detection of the

O2-O2 molecule?5. The presence of O2 is clearly seen from the weak Fraunhofer band at 628 nm6. Point 3, 4, 5, characterise Earth’s atmosphere.

Credits1. Spectroscopic Observation of the 8th Oct 2014 Total Lunar Eclipse – Richard Berry2. Atmospheric Aerosol Limb Scanning Based on the Lunar Eclipses Photometry -

Oleg S. Ugolnikov a,b,* and Igor A. Maslov a,c3. Ken Harrison – Arthor of “Astronomical Spectroscopy for Amateurs” 4. Tim Cooper – Astronomical Society of Southern Africa Ω

Newsletter Pretoria Centre ASSA August 2018 Page 8 of 15

/

Photographs and annotations above by Johan Moolman

Newsletter Pretoria Centre ASSA August 2018 Page 9 of 15

NOTICE BOARD

ScopeX 2018. Will be held at the Museum of Military History, Johannesburg, on15 September 2018 from 9am to 9pm. See https://www.scopex.co.za/

Beanies. Beanies will be offered for sale @ R40.00 each at every monthlymeeting from August onward, until they are sold out.

BLAS. I exchange newsletters with the Blackburn Leisure Astronomical Society inBritain. Their website address is: www.broughastronomy.co.uk Members who wantto receive the BLAS newsletter regularly from me (your newsletter editor) must letme know, so that I can put their e-mail addresses on a list of recipients of thatnewsletter.

One of their members, Doug Sharpe, has kept a long standing friendship with some members of the Pretoria Centre of the ASSA. He has written an article for our newsletter titled The Raspberry Pi 2B Auto Guide Computer. See the newsletter for January 2017, page 7. He and Paul Reed, also of BLAS, gave us an online talk on astrophotography at the monthly meeting on 28 November 2012.Some of Doug’s astrophotos have also appeared in our newsletter. Doug’s e-mail address is djs@thesharpes.karoo.co.uk

Newsletters of other Centres of the ASSA. I also exchange newsletters with theDurban, Hermanus, and Cape Centres of the ASSA. I have a list of e-mailaddresses of members to whom I regularly send the newsletters that I receive. Ifyou want your e-mail address to be placed on this list as well, please let me know.

Old newsletters: All old newsletters of our Centre from January 2004 onward areon our website. They contain a record of our Centre’s activities as well asastronomical information.

Database: Members are reminded that a database of the books in our library is tobe found on our website.

Feature of the month: Life on Europa? - by Pierre Lourens

Europa, one of the Galilean moons of Jupiter, offers the tantalizing possibility ofalien life elsewhere in our solar system. Europa has a thick water ice crust, and veryprobably a liquid water ocean beneath it. There are huge cracks in the crust, with darkmaterial filling them.

NASA is working on concepts for an orbiter around and lander on Europa. Thepurpose of the lander will be to search for life.

But both craft will be exposed to Jupiter’s intense radiation belts. The “radiation”consists of large fluxes of charged particles (mainly protons and electrons), originatingfrom the solar wind and trapped in helical orbits by Jupiter’s strong magnetic field. Thisexposure will shorten the life of electronic systems, unless they are well shielded.

http://earthsky.org/space/an-easier-way-to-search-for-life-on-europa?utm_source=EarthSky+News&utm_campaign=10943b529e-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-10943b529e-394671529

https://en.wikipedia.org/wiki/Europa_Lander_(NASA)#Planetary_protection Ω

Newsletter Pretoria Centre ASSA August 2018 Page 10 of 15

July 20th 2018 observing evening report- by Michael Poll & Percy Jacobs

We had a clear, but light polluted, sky; a Moon a day past first quarter, and all 5naked eye planets visible during the evening. We were 10 people attending, with somevisitors, and three telescopes.

In the west, Venus, Regulus and Mercury made a sloping line, with Mercury the lowerof the three. It was noted that the line from Venus to Regulus could be used to locateMercury for the next few days. The phase of Venus was just more than half – it is at greatestelongation east on August 17th, so we will see a half phase at our next observing evening.

The Moon was high up, but oddly enough we did not have long looks at it. Jupiterwas next to the Moon, with Io to the east of the planet, and Ganymede Europa and Callisto,in that order, to the west forming a shallow curve. Saturn was well placed for telescopicobservation, the rings are still wide open, and Titan was easily seen. Mars was well up in thesouth east later on, with only a week to go to opposition. It showed a nice big disc in ourtelescopes, but not much detail was seen.

It was explained to the visitors that the light pollution prevents us from seeing thenebulous objects (clusters for example) at their best. However we did show M7 (Ptolemy’sCluster) and M6 (the Butterfly Cluster) in Scorpius. Another cluster in Scorpius we showedwas NGC 6231, also known as the “False Comet”, which has stars streaming out of bothsides of even a low power eyepiece. Percy showed the Jewel Box. We looked at Antareswith the telescope to show the colour of a red giant.

We said that an alternative to the washed-out nebulae was to look for double stars,so we looked at Beta Scorpii, Alpha Centauri (the latter getting easier to split), and AlphaCrucis. We explained that true doubles were more common than single stars such as theSun.

Having pointed out Scorpius, it was asked if there were any other zodiacalconstellations visible, so this led to some naked eye observing. We could see Regulus, inLeo, then Libra was represented by Alpha Librae, which was right next to Jupiter. Therefollowed Scorpius and the “Teapot” of Sagittarius. The Teapot asterism seems to have beenmade popular in America, and it is a useful way to outline Sagittarius. However, for thosewho grew up in the south of England, even if the Teapot was known about at the time (whichis wasn’t), it would not have been much help as only the “lid” and the “spout” were visiblefrom there and even then, they only just scraped across the southern horizon during the(northern) summer, when it was technically twilight all night. What could be noted from thatnorthern location was the “Bow and Arrow” asterism, comprising Lambda (λ), Delta (δ) andEpsilon(ε) Sagittarii as the Bow, and Gamma (γ) as the tip of the arrow. Eta (η) Sagittarii, thesouthernmost star of the eastern quadrilateral, and one of the stars of the base of the teapotwas not visible from the south of England.

After Sagittarius in the zodiac came Capricornus, which is where Mars currentlysituated. None of the stars of Capricornus were easily visible, which led on to some starhopping. The Altair trio in Aquila was up in the east. The trio comprises Altair (α) withGamma (γ) to the left (north) and Beta (β) to the right (south). The reason for pointing outthis line of three was that, if extended to the south the line of points to Alpha and BetaCapricorni and we could just about see Alpha. Extended to the north the line points to thebright star Vega, which was just above the north eastern horizon. The other bright star notedin the north was Arcturus. We handed out some copies of Skymap.com so that people coulduse them for future reference.

As a parting shot, Percy showed Ruby Crucis, the carbon star near Beta Crucis andMichael showed NGC 6641 which is a globular cluster. This cluster might not otherwise benoted, but is very near the star G Scorpii, which lies just west of M 7. Ω

Newsletter Pretoria Centre ASSA August 2018 Page 11 of 15

Summary of presentation to be given on 22 August under “What's Up?”- by Percy Jacobs

Phases of the Moon• Dark Sky - ~1st to 11th Sept - for those who observe from sunset to midnight• Full Moon – 25th Sept (Tues) • New Moon – 9th Sept (Sun)

Planets• Mercury – West – not visible • Venus – West – evening star - ~30° above horizon in the west for the month• Mars – in the East for the month moving NE • Jupiter – in the West for the month • Saturn – in the North for the month • Neptune – in the North East for the month late at night • Uranus – in the North East for the month late at night

Planet Locations in month of November (compliments of Sky & Telescope)

Events & things of interest• Early Morning of September 16th (Sun), about 03:30, the 11.8 magnitude asteroid 80

Sappho hides a 7.2 magnitude star in Taurus. The star is HIP24403, and lies in the region of the Bull’s horns, about 5 ½ ° from Zeta Tauri

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Photographs by Johan Moolman

• 23rd Sept – Equinox - The September equinox occurs the moment the Sun crosses thecelestial equator – the imaginary line in the sky above Earth's Equator – from north to south. Ω

• Uranus & Neptune

Constellations in Sept

South

Photographs by Johan Moolman

Newsletter Pretoria Centre ASSA August 2018 Page 13 of 15

East

North

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All planets in same half of solar system on 17 August 2018 – by Neville Young

At the practical on Friday night at 23h00, all the eight planets as well as dwarf-planetPluto will be in one half of the Solar System. This means that every planet is on the same side ofthe Sun that Earth is on.

Earth will be facing this 100% populated half of the solar system at 23h00 which meanswe have Uranus in Aries rising very low in the east, then continuing westward will be Neptune inAquarius, Mars in Capricorn, Pluto and Saturn in Sagittarius and finally Jupiter in Libra settingvery low in the east.

In fact, even though they are inner planets, Venus and Mercury are in that same half ofthe solar system. We can still see Venus until 21h00 and Mercury will rise at 05h45 the nextmorning.

To be clear - the outer planets will all be 'VISIBLE' above our horizons at 23h00 on Fridayevening, BUT they have all been in the same half of the solar system for the past few weeks. Inabout a week, Mercury will speedily orbit around to spend a lonely time in the other half of thesolar system for about 6 weeks when it will rejoin its planetary compatriots in the over-populatedhalf. Ω

Newsletter Pretoria Centre ASSA August 2018 Page 15 of 15

Summary of “Beginner’s Corner” to be presented on August 22nd 2018- by Michael Poll

December 2020 sees what is known as “The Great Conjunction” – after a 20-yearchase, Jupiter catches up with Saturn. But what do we mean by “conjunction”? Quiteoften if two planets, a planet and a star, or the Moon and a star or planet, are close toeach other, we say “they are in conjunction”. But what is the strict definition of“conjunction’?

Astronomically speaking, there is conjunction in right ascension and conjunctionin ecliptic longitude. And what about a triple conjunction? This presentation explainsconjunctions and looks at some historical and future planet/planet conjunctions, andplanet /star conjunctions. As well as the Great Conjunction of 2020, events to bedescribed include the triple conjunction of Jupiter and Saturn in 1981, and thecircumstances for triple conjunctions of Venus and Jupiter to occur. Ω

Pretoria Centre committeeChairman Johan Smit 072 806 2939 johanchsmit@gmail.com

Vice Chairman Michael Moller 082 789 8968 mmoller2k@gmail.com

Secretary Michael Poll 074 473 4785 pollmnj@icon.co.za

Newsletter Editor Pierre Lourens 072 207 1403 pierre.lourens@vodamail.co.za

Librarian and

Webmaster Danie Barnardo 084 588 6668 daniebar@webmail.co.za

Curator of Instruments Johan Smit 072 806 2939 johanchsmit@gmail.com

Public Relations Officer Fred Oosthuizen 072 373 2865 fredo@oostvallei.co.za

Observing Coordinator Percy Jacobs 060 883 8106 percymj@iafrica.com

Treasurer and

Membership Secretary Michelle Ferreira 073 173 0168 michellem.ferreira@standardbank.co.za

Member Bosman Olivier 082 883 1869 bosman.olivier@gmail.com

Astronomy basics: Celestial Sphere, Ecliptic, and the Constellations

https://www.youtube.com/watch?v=96guilZWFHk